There is a variety of available one-way coupling designs adapted to specific needs. In one-way coupling designs using sprag-type clutches for hold-back applications, one race is always stationary. The function of a hold-back clutch is to permit rotation of the non-stationery race in one direction only, and to prevent any rotation in the reverse direction at any time. Hold-back is the name given to the back-stop clutch when applied to an overrunning installation wherein the sole function of the clutch is that of militating against any retrograde movement of the rotating elements. Such couplings find use in a variety of applications and frequently must function reliably under extreme adverse conditions. One of the typical applications is in nuclear energy systems wherein the associated equipment and bearings are generally inaccessible.
Lubrication is, in the above application, an extremely difficult problem. Certain couplings may have an external pump for providing lubricant and such an arrangement may be highly satisfactory so long as the pump and related equipment are functioning satisfactorily. One shortcoming with previous coupling designs using an external lubricant supply is that it has limited ability to operate satisfactorily when such supply is terminated. Since loss of lubricant often occurs when the coupling is subjected to other difficult operating conditions, this is a serious shortcoming.
It is an object of the present invention to provide a hold-back coupling with an internal lubricant recirculation arrangement to provide satisfactory operation under extended adverse operating conditions.
It is a further object of the invention to provide such a coupling which is as simple and compact as possible to provide a relatively low cost solution to the foregoing problems.